Porous particles of calcium carbonate and method for the preparation thereof

A method for imparting porosity to particles of pulverized calcium carbonate mineral which comprises the steps of:

• (a) blending particles of said calcium carbonate mineral, of which the particle diameter is in the range from 1 .mu.m to 20 .mu.m and the average particle diameter is in the range from 5 .mu.m to 15 .mu.m, with from 0.1 to 0.3% by weight of particles of a porosity-forming agent selected from the group consisting of alkali metal halides, alkaline earth metal halides and mixtures thereof to give a uniform powder blend mixture consisting essentially of particles of said calcium carbonate and said agent;
• (b) calcining the solid phase powder blend at a temperature in the range from 800.degree. C. to 1000.degree. C. to decarbonate the solid phase calcium carbonate mineral particles into solid phase particles of calcium oxide having pores developed therein;
• (c) slaking the solid phase particles of calcium oxide with steam to convert the calcium oxide particles into solid phase particles of calcium hydroxide;
• (d) drying the particles of calcium hydroxide at a temperature in the range from 100.degree. C. to 350.degree. C.;
• and
• (e) carbonating the dried solid phase particles of calcium hydroxide with carbon dioxide gas at a temperature in the range from 600.degree. C. to 750.degree. C.